Under the 3rd Generation Partnership Project (3GPP), the W-CDMA scheme has been standardized as a third generation cellular mobile communication scheme, and is currently in service. HSDPA, which has even higher communication speeds, has also been standardized and is currently in service.
Meanwhile, under the 3GPP, the evolution of third generation radio access (Long Term Evolution: LTE or Evolved Universal Terrestrial Radio Access: EUTRA) has also been standardized, and LTE service has begun. The orthogonal frequency division multiplexing (OFDM) scheme, which is robust against multipath interference and suited for high-speed transmission, has been adopted as an LTE downlink communication scheme. Furthermore, considerations pertaining to cost and power consumption of terminal devices have led to the adoption of the discrete Fourier transform (DFT)-spread OFDM scheme based on the single-carrier frequency division multiple access (SC-FDMA) that allows for a reduction in the peak to average power ratio (PAPR) of transmit signals, as an uplink communication technique.
Additionally, under the 3GPP, discussions about LTE-Advanced (or Advanced-EUTRA), which represents further evolution of LTE, are ongoing. In the LTE-Advanced, it is envisaged to use bands having a maximum bandwidth of up to 100 MHz for each of uplink and downlink, to perform communication at maximum transmission rates of 1 Gbps or more for downlink, and 500 Mbps or more for uplink.
In the LTE-Advanced, it is contemplated to achieve a band of a maximum of 100 MHz by binding together multiple bands which are compatible with LTE, so as to be able to accommodate LTE terminal devices as well. Note that in the LTE-Advanced, a single LTE band of 20 MHz or narrower is called a component carrier (CC). A component carrier is also called a cell. Binding together bands of 20 MHz or narrower is termed carrier aggregation (CA) (NPL 1).
Meanwhile, in the LTE-Advanced, issues relating to lowering the cost of terminal devices that correspond to specific categories, such as machine type communication (MTC) or machine type communication (M2M), are also under examination (NPL 2). Hereinbelow, MTC/M2M terminal devices, or MTC/M2M communication devices will also be referred to as a machine type communication user equipment (MTCUE).
In order to realize low-cost MTCUE while maintaining backward compatibility with systems compliant with the LTE standard and LTE-Advanced standard, cost reduction methods have been proposed, for example, by narrowing the transmission/reception bandwidth, reducing the number of antenna ports/number of RF chains, lowering the transmission/reception data transfer rate, adopting a half-duplex frequency division duplex scheme, reducing the transmit/receive power, and extending the discontinuous reception interval. It has also been proposed that reducing the maximum bandwidth of MTCUE transmission/reception RF circuit or transmission/reception baseband circuit would be effective as a method for realizing low-cost MTCUE.
In MTC, cost reductions are not the only issue being studied, and coverage enhancement for enhancing the transmission/reception range of MTCUE is also currently a subject of study. In order to enhance coverage, it is contemplated for a base station device to repeatedly transmit downlink data or a downlink signal to MTCUE, and for MTCUE to repeatedly transmit uplink data or an uplink signal to the base station device (NPL 3).
For example, the base station device repeatedly transmits multiple times a physical broadcast channel PBCH to the MTCUE within 40 ms. Also, in a random access procedure, the MTCUE repeatedly transmits the same random access preamble, using multiple resources of a random access channel PRACH. Having received the random access preamble, the base station device repeatedly transmits a random access response message. Note that the base station device notifies MTCUE within a cell through a broadcast channel BCH, or individually notifies MTCUE, of the number of repetitions (or a parameter associated with the number of repetitions (also termed the repetition level, cell enhancement level, or the like) (NPL 3).
For example, the number of transmission repetitions of random access preamble or the number of transmission repetitions of random access response message is notified through the broadcast channel BCH. Another topic of ongoing study is how to enable MTCUE to select a single number of transmission repetitions from among multiple different numbers of transmission repetitions, where the numbers of transmission repetitions of random access preambles include multiple different numbers of transmission repetitions.